A conventional altitude display for a terrain awareness system for a given aircraft provides a pilot with a visual display of the terrain having an altitude higher than the aircraft, as well as the terrain within some distance (e.g. 2000′) below an aircraft. If it appears that the aircraft is going to hit or travel relatively close to terrain, various alerts and warnings are generated. See, e.g., U.S. Pat. No. 6,138,060 to Conner et al. As used herein, warnings relate to more threatening conditions than alerts. Each may include audible, visual or other type of indications to a user.
One problem with conventional systems is false or nuisance alerts and warnings may be generated as the aircraft is preparing to land at a runway. That is, as the aircraft descends it will naturally appear to be headed towards terrain (the runway), and nuisance alerts and warnings may be generated. Furthermore, the terrain may still be displayed on the aviation display unit. As a result, the screen may be cluttered with non-threatening terrain data during landing.